1. Field of the Invention
The present invention relates to a touch panel liquid crystal display, and more particularly to a liquid crystal display with a touch panel that does not overlap with a display area of a liquid crystal panel but is still capable of obtaining a non-touch area.
2. Description of the Related Art
A touch panel device reads an input operation of a user by a coordinate value and inputs data. Touch panels are deposited on a display device, e.g., a liquid crystal display (LCD) and are often used, for example, in bank automatic teller machines (ATMs). Touch panels generate a voltage or electric current signal corresponding to the position where it is pressed with a stylus pen or finger and thereby input graphic or other data assigned by the user. Recently, analogue input type resistance film system touch panels have been integrated with liquid crystal panels of flat panel display devices.
An active matrix liquid crystal display having a touch panel deposited thereon displays a picture corresponding to a video signal, similar to a television signal, on a picture element pixel matrix where pixels are arranged at crossings of gate and data lines. Each pixel includes a liquid crystal cell that controls the amount of light transmitted in accordance with a data signal voltage level from the data line. A thin film transistor (TFT) is provided at crossings of the gate and data lines, responds to scanning signals (gate pulse) from the gate line, and switches data signals such that they are transferred to a liquid crystal cell.
A liquid crystal display requires a plurality of driving integrated circuits (D-ICs) that are connected to both the data and gate lines to supply data signals and scanning signals to the data lines and the gate lines, respectively. D-ICs are conventionally provided between a printed circuit board (PCB) and a liquid crystal panel, are responsive to control signals supplied from the PCB, and supply data scanning signals to the data and gate lines of the liquid crystal panel. In the Tape Automated Bonding (TAB) method, a method commonly used to mount D-ICs, the display area of the panel can be made large and the mounting process is simple.
Referring to FIG. 1, a liquid crystal display with a conventional touch panel includes a liquid crystal panel 40 and a touch panel 10 on the liquid crystal panel 40.
The liquid crystal panel 40 includes a lower substrate 32 where a thin film transistor (TFT) array (not shown) and an alignment film (not shown) are sequentially formed; an upper substrate 34 where a color filter array (not shown), a common electrode (not shown), and an alignment film (not shown) are sequentially formed; liquid crystal (not shown) injected into a gap formed by a spacer and a sealant (not shown) between the upper substrate 34 and the lower substrate 32; an upper polarizing plate 36 adhered to the upper surface of the upper substrate 34; and a lower polarizing plate 38 adhered to the lower surface of the lower substrate 32. A black matrix 42 is formed is formed in a non-display area that is at the outer edge of the upper substrate 34. The black matrix 42 prevents visible light from radiating to the outside.
A drive circuit portion for driving such a liquid crystal panel 40 includes a PCB 46, a tape carrier package (TCP) 44 connecting the liquid crystal panel 40 and the PCB 46, and a D-IC 48 mounted on the TCP 44. The TCP 44 is adhered to the lower substrate 32 by an anisotropic conductive film (ACF). The D-IC 48 mounted on the TCP 44 supplies a driving signal in accordance with a control signal from the PCB 46 to the liquid crystal panel 40. The touch panel 10 provides the location of information for a user to select the information displayed on a screen, and displays the information on a display area of the liquid crystal panel 40.
With reference to FIG. 2, principles of operation of the touch panel 10 are explained. Electrodes 50A and 50B aligned in the X direction and electrodes 52A and 52B in the Y direction of the touch panel 10 are connected to an output portion 54.
Voltage is alternately applied to the electrodes 50A and 50B in the X direction and electrodes 52A and 52B in the Y direction to detect the location X and Y of a contact point created by a user. When voltage is applied to the X direction electrodes 50A and 50B, voltage is not applied to the Y direction electrodes 52A and 52B. A fixed amount of voltage that is applied to the upper X direction electrode 50A and the lower X direction electrode 50B is grounded. Thus, an equipotential is applied to the touch panel 10 in the X direction. Herein, the electric current corresponding to the voltage of the contact point contacted by the user flows to the Y direction electrodes 52A and 52B to output the Y coordinate of the contact point to the output portion 54.
In the same way, when voltage is applied to the Y direction electrodes 52A and 52B, voltage is applied to the X direction electrodes 50A and 50B. At this moment, a fixed amount of voltage is not applied to any one of the Y direction electrodes 52A and 52B and another electrode is grounded. Thus, an equipotential is applied to the touch panel 10 in the Y direction. Electric current corresponding to the voltage of the contact point contacted by the user flows to the X direction electrodes 50A and 50B to output the X coordinate of the contact point to the output portion 54.
Likewise, the touch panel 10 detects location information inputted from the outside by detecting the X and Y coordinates of the contact point.
FIGS. 3A to 3D illustrate a method of fabricating a liquid crystal display having a touch panel.
Referring to FIG. 3A, spacers (not shown) are dispersed between the lower substrate 32 including the TFT array and the upper substrate 34 where the color filter array is formed. Subsequently, the upper substrate 34 and the lower substrate 32 are aligned and joined together. The black matrix 42 is formed for preventing light leakage in the non-display area of the upper substrate 34. Liquid crystal (not shown) is injected into a gap provided by the spacer between the upper substrate 34 and the lower substrate 32.
Subsequently, the lower polarizing plate 38 is adhered to the lower surface of the lower substrate 32, as illustrated in FIG. 3B. Subsequently, as shown in FIG. 3C, the upper polarizing plate 36 is adhered to the upper surface of the previously provided upper substrate 34 and the touch panel 10 is adhered to the upper surface of the polarizing plate.
Then, as shown in FIG. 3D, the TCP 44 connects a PCB and a pad portion of the lower substrate 32. The ACF is prepressed and fixed on the pad portion of the lower substrate 32. The TCP is punched 44 to provide holes for transporting and for an integrated circuit. After punching the TCP 44, an alignment mark of the TCP 44 and an alignment mark of the lower substrate 32 are aligned and then the TCP 44 is pressed to be fixed on the ACF. The resin of the ACF is hardened after the prefixed TCP 44 is heat-treated and pressed. Conductive balls in the inside of the ACF electrically connect the TCP 44 and the pad portion of the lower substrate 32.
A flow chart of such a process procedure is illustrated in FIG. 4. As shown in FIG. 4, after joining the upper substrate and the lower substrate together (S41 ), the lower polarizing plate is adhered to the lower surface of the lower substrate (S42). After that, the touch panel to which the upper polarizing plate is adhered is mounted on the upper surface of the upper substrate (S43). And then, the pad portion of the lower substrate is joined to the TCP in a TAB process (S44). By this method, a liquid crystal display having a touch panel is fabricated.
In such a liquid crystal display, a non-touch area 20 exists in the touch panel 10 as shown in FIG. 5A. The non-touch area 20 is composed of an adhesion area 20A for adhering an upper film of the touch panel to a lower film, and an outer area 20B to which it is impossible to input user information when the user presses the touch panel 10. Because the touch panel 10 is provided on the liquid crystal panel 40, the information of the display area is not operable in the area corresponding to the non-touch area 20 of the touch panel 10. Accordingly, the area where the liquid crystal panel 40 can be controlled is decreased due to the presence of unused area 40A in the liquid crystal panel 40.
Furthermore, when the non-touch area 20 of the touch panel 10 is provided to not overlap with the display area of the upper substrate 34 as illustrated in FIG. 5B, the non-touch area 20 of the touch panel 10 projects from the side of the upper substrate 34. Accordingly, the touch panel 10 covers the alignment mark arranged on the lower substrate 32 and occupies the position where the TCP 44 is to be formed. As a result, it becomes difficult to adhere to the TCP 44 to the pad portion of the lower substrate 32.